<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<script type="text/javascript" src="js/demo01.js" >
//			alert('hahahah'); //引入外部js文件标签不可以写代码
		</script>
		<script>
			//变量 内存中临时存储的空间
			var my_test = '张三';
			
			document.writeln('<br/>'+my_test);
			
			document.writeln("水电费水电费水电费水电费,\"水电费水电费\"水电费水电费");
			
			var PI = 2.1415926;
			document.writeln(Math.PI);
			//var a,b,c; //不推荐
			  var a;
			  var b;
			  var c;
			  
			var $aaa = 1;
			
			var sss = 0;
		</script>
	</head>
	<body>
	</body>
</html>
